Using Space Engine, I created an asteroid with earthlike atmosphere. Hope you like it:

The asteroid is very near it's star, a M2V. It's so close that this atmosphere only exist because the surface itself is being evaporated. And most of what is in the air is the oxygen from the rocks. And this too won't last much around the asteroid. You can see the atmosphere is irregular, some parts of the surface have thin air and other parts thicker air.